Effects of Changes in Regional Body Composition on Physical Function in Older Adults: A Pilot Randomized Controlled Trial

Abstract

Background/objective: Obesity exacerbates age-related physical disability; however, observational studies show that any weight loss in old age is associated with greater risk of mortality. Conversely, randomized controlled trials in older adults show that weight loss is beneficial. The discrepancy may be due to weight loss intention and differential changes to regional body composition. The purpose of this research was to evaluate the independent role of regional body composition remodeling in improving physical function.

Design: Pilot Randomized Controlled Trial.

Setting: Community based research center.

Participants: Thirty-six community dwelling, overweight to moderately obese (BMI 28.0-39.9 kg/m2) older adults (age 70.6±6.1 yrs).

Intervention: Physical activity plus weight loss (PA+WL, n=21) or PA plus successful aging (SA) education. PA consisted primary of treadmill walking supplemented with lower extremity resistance and balance training. The WL program was based on the Diabetes Prevention Project and aimed at achieving a 7% weight loss by cutting calories, specifically those from fat.

Measurements: At baseline, 6- and 12-months, body composition was measured using computerized tomography and dual x-ray absorptiometry. Abdominal visceral (VAT) and thigh intermuscular (IMAT) adipose tissue were quantified. Physical function was assessed using the short physical performance battery (SPPB).

Results: Separate multivariable linear regression models with both groups combined demonstrated that decreases in IMAT and VAT were significantly associated with improvements in SPPB (P<0.05) independent of change in total fat mass. PA+WL improved SPPB scores from baseline (0.8±1.4, P<0.05), whereas PA+SA did not; however no intergroup difference was detected. Of note, these effects were mainly achieved during the intensive intervention phase.

Conclusion: Decreases in IMAT and VAT are important mechanisms underlying improved function following intentional weight loss plus physical activity.

Trial registration: ClinicalTrials.gov NCT00714506.

Figure 1.

Screening, Randomization and Follow-Up Flow Chart

Figure 2.. 12-Month Changes in Specific Fat Depots of the Thigh and Abdomen Measured by Computed Tomography.

Data are presented as mean percent change in cross-sectional area, except muscle density, which was measured in Hounsfield units. The PA+WL group experienced significant decreases in all depots (all P<0.05) except muscle density – which increased slightly in both groups. The PA+SA group experienced a significant decrease in IMAT only (P<0.05). A significant intergroup difference exists for change in VAT only (P<0.05). *Denotes a significant change from baseline (P<0.05). Abbreviations: SUBQ: subcutaneous, VAT: visceral adipose tissue, IMAT: intermuscular adipose tissue, BL: baseline, PA+WL: physical activity plus weight loss, PA+SA: physical activity plus successful aging education.

Figure 3.. Short Physical Performance Battery Score (Panel A) and 400 Meter Walk Time (Panel B) by Time Point and Intervention Group

Panel A. Change in SPPB score by time point and stratified by intervention group. Data are means and the error bars represent standard errors. The PA+WL group experienced a near significant improvement from baseline to 6-months (0.6±1.3, P=0.06, n=21) and this change became significant at 12-months (0.8±1.4, P=0.03, n=18). The PA+SA group did not experience any significant changes, but there were no significant intergroup differences in regard to change in SPPB score. *Denotes a significant change from baseline (P<0.05). Abbreviations: SPPB: short physical performance battery, PA+WL: physical activity plus weight loss, PA+SA: physical activity plus successful aging education. Panel B. Time to walk 400m at usual pace in seconds, by time point and stratified by intervention group. Data are means and the error bars represent standard errors. The PA+WL group experienced a significant improvement (P<0.05) from baseline to 6-months, but this improvement reverted back to non-significance at 12-months. The PA+SA group did not show any significant changes and there were no significant intergroup differences in regard to 6- or 12-month change in 400m walk time. *Denotes a significant change from baseline (P<0.05). Abbreviations: PA+WL: physical activity plus weight loss, PA+SA: physical activity plus successful aging education